Our minds think visually more often than we are aware. We tend to believe what we see, unless there is information to make us doubt it.
But we should not trust our minds so much, as our own minds can often fool us.
An impossible object is an optical illusion made in two dimensions that would be impossible in three dimensions.
The Penrose Triangle is a drawing of an impossible three dimensional object on a two dimensional surface plane. It is an impossible shape to exist in Euclidean three dimensional space. We want to make the adjacent edges join in a logical way, so a real three dimensional space can be imagined, but it cannot.
Our mind tries to interpret the Penrose Triangle as a three dimensional object in space, rather than interpreting it as a two dimensional object drawn on the paper plane. It is interesting to note that the Impossible Triangle still seems to want to be three dimensional, even after the early visual realisation that it cannot.
The Triangle was first created by the Swedish graphic artist Oscar Reutersvard, in 1934. Oscar Reutersvard used a series of cubes to make the sides of his triangle.
It was then drawn independently by the mathematician and philosopher Roger Penrose in the 1950’s, as an excellent example of an impossible object.
Later the Dutch artist M.C.Escher used the illusion in many of his prints, for example The Waterfall, a lithograph from 1961.
Tom McPherson's blog on art and creativity.